1. Field of the Invention
The present invention relates to a recycling method of an olivine-based cathode material for a lithium secondary battery, a cathode material fabricated therefrom, and a cathode and a lithium secondary battery including the same. More particularly, the present invention relates to a method for synthesizing a cathode material including LiFePO4 by chemically treating lithium secondary battery cathode scraps including LiFePO4 to synthesize amorphous FePO4.XH2O and crystalline FePO4.2H2O (metastrengite), and then using the synthesized crystalline FePO4.2H2O (metastrengite). The present invention also relates to a cathode material fabricated therefrom, a cathode and a lithium secondary battery including the same.
2. Discussion of Related Art
A lithium secondary battery is a secondary battery having excellent performances, such as high capacity, high output, long service life, and the like, and is widely used in small electronic products such as electronic devices, laptops, cell phones, and the like. In particular, as interests in green growth and new renewable energy such as solar energy, wind power, and the like have recently increased, a need for a large-capacity lithium secondary battery for an electric vehicle, an energy storage system, and the like is expected to sharply increase.
As a cathode material for a lithium secondary battery, various kinds of materials have been developed, and along with LiCoO2, a ternary cathode material (LiCo1/3Ni1/3Mn1/3O2) and the like in the related art, recently, a LiFePO4 cathode material that is an olivine-based material has been recently highlighted as a large-capacity lithium secondary battery for an electric vehicle and an energy storage system. In particular, since the LiFePO4 cathode material is cheaper than other cathode materials, the commercialization of a large-capacity lithium secondary battery using LiFePO4 as a cathode material is expected to be within reach in the near future.
As described above, the lithium secondary battery market and industry are expected to sharply increase, but lithium (Li) as an essential metal of the cathode material or related compounds are not found in Korea, and thus are entirely imported from other countries and used. Therefore, in countries having no natural resources such as Korea, it is necessary to recover and recycle cathode material scraps produced in a manufacturing process of a lithium secondary battery, or lithium secondary battery cathode materials disposed of after use.
As a method of extracting or recovering various metals such as lithium and the like or compounds from a lithium secondary battery cathode material in the related art, a process of recovering a cathode material by dissolving the cathode material separated from a waste lithium battery in a strong acid such as hydrochloric acid (HCl), sulfuric acid (H2SO4), nitric acid (HNO3), or the like, then neutralizing the resulting solution with an alkali, and precipitating cobalt (Co), nickel (Ni) and the like with hydroxide is used, or a method of separating a metal such as cobalt, manganese, nickel, and the like from a liquid in which the cathode material is dissolved by a solvent extraction method is used.
As described above, in the method of treating a cathode material in the related art, while it is an object to recover heavy metals such as cobalt, nickel, and the like, there is not much of an interest in lithium because lithium is cheaper than cobalt and nickel. However, lithium and related resources are very limited and a large-capacity lithium secondary battery for an electric vehicle and an energy storage system is likely to use a phosphate-based LiFePO4 which does not include cobalt or nickel as a cathode material, and thus more concentration will likely be placed on the recovery or recycling of lithium or related compounds in the future.